High-resolution and large dynamic range nanomechanical mapping in tapping-mode atomic force microscopy

High spatial resolution imaging of material properties is an important task for the continued development of nanomaterials and studies of biological systems. Time-varying interaction forces between the vibrating tip and the sample in a tapping-mode atomic force microscope contain detailed information about the elastic, adhesive, and dissipative response of the sample. We report real-time measurement and analysis of the time-varying tip-sample interaction forces with recently introduced torsional harmonic cantilevers. With these measurements, high-resolution maps of elastic modulus, adhesion force, energy dissipation, and topography are generated simultaneously in a single scan. With peak tapping forces as low as 0.6?nN, we demonstrate measurements on blended polymers and self-assembled molecular architectures with feature sizes at 1, 10, and 500?nm. We also observed an elastic modulus measurement range of four orders of magnitude (1?MPa to 10?GPa) for a single cantilever under identical feedback conditions, which can be particularly useful for analyzing heterogeneous samples with largely different material components.     

Shielding study on iron and concrete assemblies of bremsstrahlung photons and photoneutrons from copper target bombarded by 18, 28 and 38 MeV electrons

Following the angular distribution measurements of bremsstrahlung photons and photoneutrons, we measured the distributions of photon and neutron dose rates in the iron and concrete assemblies using a copper target bombarded by 18, 28 and 38 MeV electrons at the electron linear accelerator (linac) of Hokkaido University. In this experiment, seven types of shielding assemblies of iron and concrete layers were used and the photon and neutron dosemeters were inserted into the assemblies to get the depth–dose distribution. The measured results were compared with the results calculated using the Monte Carlo code MCNP5 to verify the calculated results. The calculated results of the ambient dose equivalent rates were in agreement with the measured results within 30% accuracy. Since no work on the radiation behavior in the shielding wall of medical linac room has ever been reported, this work gives valuable benchmark data for the detailed shielding design with high accuracy.     

Designing data center network by analytic hierarchy process

The demand for delivery services for large-sized content such as video has increased dramatically, and the use of cloud computing services in which users can use IT services via networks has also increased. To provide these services with high quality and high reliability, ISPs need to carefully design network topology and the positions of data centers. However, network topology and data center location strongly affect various evaluation criteria, such as cost, path length, and reliability; therefore, these criteria with different respective units need to be considered simultaneously when designing a data center network. The analytic hierarchy process (AHP) is a way to make a rational decision considering multiple criteria. This paper proposes to design data center networks by evaluating both network topology and data center locations simultaneously using AHP and also shows the numerical results of applying the proposed design method to the three areas of Japan, USA, and Europe. We investigate the properties of desirable data center networks in these three areas, and compare the results with those obtained by the enumeration method.     

Robust gain-scheduled control for vibration suppression

Limited control authority is a key issue in the field of structural control and is a major research area since most of the practical control problems are dominated by constraints on the control signal. The paper presents a simple and practical gain-scheduled controller design procedure for active vibration suppression of a three-storey flexible structure. First, system identification experiments are performed and the plants uncertainty is derived. Next, robust controller design with constraint on the control signal is presented. For a better trade-off between control performance and control constraint a gain-scheduling approach is investigated. Stability analysis of the gain-scheduled controller is analysed using a parameter-independent Lyapunov function (quadratic stability) as well as a parameter-dependent Lyapunov function (biquadratic stability). Finally, the gain-scheduled controller is tested experimentally when the flexible structure is excited with a scaled historical earthquake record (1940 El Centro record). Successful experimental results show that the proposed robust gain-scheduled control approach offers good performance in the case of control authority limitation.Nomenclature M mass matrix - C damping matrix - K stiffness matrix - q relative displacement vector to base - m_a active mass - active mass acceleration - ground (base) acceleration - K_gap transfer gain of the displacement sensor - K_acc transfer gain of the acceleration sensor - K_AMD transfer gain of the active mass damper - _id frequency range of system identification experiments - r control reference - u control signal - d external disturbance - y control output - e control error - x state vector - p(t) time-varying parameter - N_p parameter boxs dimension - V(x) Lyapunov function - V(x,p) parameter-dependent Lyapunov function - largest parameter box where quadratic stability holds - S(s),T(s) sensitivity and complementary sensitivity transfer functions - G_n(s),G(s) transfer function of nominal and real plant - K_rate rate feedback gain - P_n(s) transfer function of nominal plant modified by rate feedback - P(s) transfer function of real plant modified by rate feedback - G_red transfer function of the reduced-order plant - _m(s) multiplicative uncertainty - W_S(s),W_T(s) performance and robustness weighting functions - G_c(s) controllers transfer function - G_c1(s),G_c2(s) transfer function of robust controller for vertex 1 and vertex 2 - G_cs(p,s) transfer function of the gain-scheduled controller - u_A amplitude of the control signal - K_min,K_max minimum and maximum controller gain - K(p) scheduled controller gain - J₁,J₂,J₃,J₄,J₅ performance evaluation parameters     

Ferroelectric distortion and electronic structure in Bi4Ti3O12

The ferroelectric phase transition in Bi₄Ti₃O₁₂ has been investigated through Rietveld analysis of high-resolution neutron powder diffraction and electronic structure calculations. The structural and electronic analyses show that the traditional model based on the stereoactive lone-pair 6s electrons of Bi³⁺ is not sufficient to explain the structural distortions in the ferroelectric state. It is strongly suggested that the hybridization of the Bi 6p and the O 2p in the perovskite layers is the trigger of the ferroelectric transition in Bi₄Ti₃O₁₂, and that this orbital interaction is responsible for stabilizing the ferroelectric displacements in the perovskite layers.     

Experimental study on fuel-discharge behaviour through in-core coolant channels

In core-disruptive accidents of sodium-cooled fast reactors, fuel discharge from the core region reduces the possibility of severe re-criticality events. In-core coolant channels with large hydraulic diameters, such as the control-rod guide tube and a concept of the Fuel Assembly with Inner Duct Structure have a potential to provide effective fuel-discharge paths if effects of sodium in these paths on molten fuel discharge are limited. Two series of experiments were conducted to investigate fuel-discharge behaviour through the sodium-filled channels. In the first series of experiments, an alloy with low melting temperature was ejected into a water channel to clarify dominant phenomena for melt discharge through the coolant-filled channel and to develop methodologies for evaluating the effects of coolant on melt discharge. In the second series of experiments, a molten alumina was discharged through the sodium-filled channel in order to verify the applicability of the knowledge and evaluation methodologies obtained in the first series of experiments to the sodium-filled channel. These series of experiments showed that the discharge path can be entirely voided by the vaporisation of a part of the coolant at the initial melt discharge phase that this is followed by coolant vapour expansion and that melt penetrates significantly into the voided channel. Preliminary extrapolation of the present results to the in-core coolant channel suggests that the effects of the sodium on fuel discharge are limited and, therefore, in-core coolant channels will provide effective fuel-discharge paths for reducing neutronic activity.     

野外试验场场址土壤蒸发量的计算

为了确定野外试验场场址由地表向地下土壤渗入的水量,必须计算场址的地表蒸发量.在野外试验场安装了环境气象自动监测装置,每10分钟自动记录一次监测数据,观测历时二年多.将所获取的气象数据和有关参数用Penman法、能量平衡法、迭代法和湍流相关法四种方法计算了土壤蒸发量,计算结果表明,试验场址的土壤年蒸发量与降水量基本一致,在400～600mm/a之间.     

野外试验场浅层水文地质调查

在现有资料的基础上,通过区域水文地质调研、试验场浅部含水层水文地质钻探试验、地下水水位动态观测和地下水水化学成分分析,给出了本院野外试验场浅部含水层的分布状况,包括各含水层的埋深、厚度、固相介质组成及相应的地下水动力学参数、地下水流向与水力坡度及地下水水化学特征.     

Relationship between the skin permeation movement of propranolol and skin inflammatory reactions

We studied inflammatory reactions induced by dermal application of the beta-blocker propranolol (PRL) in ethanol to guinea pigs in order to elucidate the relation of the reactions with the cumulative PRL permeating amount through the stratum corneum or the PRL content in the stripped skin, and to investigate the chemical mediators responsible for the reactions. The cumulative PRL permeating amount through the stratum corneum increased rapidly up to 2 h after dermal application, then increased linearly with time up to 24 h after application. Visual observation revealed formation of erythema and edema at the applied site of PRL, and histopathological examination revealed infiltration of pseudoeosinophiles of dermis and epidermis and degeneration/necrosis of epidermis. In general, it was considered that the duration and the extent of these reactions were dependent on the PRL dosage and application time. It was expected that the cumulative PRL permeating amount through the stratum corneum could be used to predict possible inflammatory reactions during development of transdermal drug delivery systems. On the other hand, contact of PRL with guinea pig skin tissues released histamine, and intradermal injection of PRL caused an increase of capillary permeability at the site of application. Also, the inhibitory effects of anti-inflammatory agents (diphenhydramine, dexamethasone, indomethacin, cyproheptadine hydrochloride, CV3988 and AA-861) to PRL-induced erythema formation demonstrated that histamine and prostaglandins were responsible for the inflammatory reactions induced by PRL.